High security chain tried and tested in the streets of new yorkfour sided trapezoidal chain links made from triple heat treated boron manganese steel for ultimate strengthnarrow inner width of individual links prevent leverage attacksev series 4 disc lock has flat keyway locking mechanism for extensive holding power and high picking resistance and an ovalised extra strong crossbar to withstand pull force and cut force14 mm hardened steel shacklesliding dustcover protects and extends cylinder lif